Online performance monitoring and fault diagnosis technique for direct current motors as used in printer mechanisms

ABSTRACT

A technique that performs both real time and online monitoring and fault diagnosis during the operation of mechanical equipment with at least one direct current motor. The method described includes the steps of selecting conditions of operation that correspond to acceptable equipment functioning, and monitoring these conditions continuously during the operation of the equipment. When a fault develops, the monitoring routine initiates a diagnosis subroutine which identifies the component causing the fault and establishes an error message to indicate the faulty component, prior to the initiation of equipment shutdown procedures.

This is a division of Ser. No. 303,715 filed Jan. 27, 1989.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention, generally, relates to motor control systems and,more particularly, to a technique for effectively functioning as anonline monitor of the performance of a direct current motor and forperforming an online diagnosis of any fault detected beforeparticipating in a shutdown procedure.

2. Description of the Prior Art

By carefully studying the types of the failures that occur in a directcurrent motor driven mechanism, particularly as used in a printer for acomputer system, it is possible to develop a list of those operationsthat should be monitored. The monitoring of such operations can revealconditions or problems that lead to failures, and past efforts have allcaused system shutdown before such failures occur.

Clearly, a system shutdown is preferable, when compared with a systemfailure. However, it has been found that a system shutdown can cause aproblem in diagnosing the cause and, therefore, in providing thenecessary preventive maintenance, because all too often it is an inputdata error that caused the shutdown and not a fault with the system.Therefore, what is needed is a way to diagnose the situation before thesystem shutdown procedure is initiated.

A U.S. Pat. No. 4,733,343 to Yoneda et al. describes a troubleidentification scheme in connection with a numerical control machine, sothat the machine may be stopped with a controlled "slow-down". Oncestopped, however, repair of the trouble is not provided for.

In a Federico et al. U.S. Pat. No. 4,514,846 that issued in 1985, thereis described a way of isolating the detected fault to a particularcontrol board for later study and, hopefully, diagnosis of the cause.These inventors recognize that it is difficult to diagnose the cause ofa fault at a later time, and so, there is provided this system ofisolating a fault to a particular control board as a way of developing ahistory of where the faults are occurring.

There is a U.S. Pat. No. 4,179,732 that issued in 1979 to Khan et al.which also recognizes the clear advantages of having the diagnosisfunction performed, but it teaches that it must be done off-line. Seecolumn 11, lines 20-29. This teaching is a self diagnostic capability inprinter microprocessor architecture that is done after the function isterminated and the printer system is driven off-line.

Of the U.S. patents assigned to the same Assignee as the presentinvention, U.S. Pat. No. 4,287,461; U.S. Pat. No. 4,452,136; U.S. Pat.No. 4,570,110; and U.S. Pat. No. 4,591,969 concern various aspects ofmotor control systems. However, of these prior patents, only the '136patent teaches the use of a diagnostic capability, but that is anoff-line arrangement. A printer control microprocessor is described ascontaining a diagnosis capability that is selected manually and executedoff-line. See column 6, line 45 to column 7, line 5.

In U.S Pat. No. 4,730,164 to Daido et al., a diagnosis routine isdescribed for detecting an abnormal condition in a stepping motor, butit must be done at initialization only, that is, before the controlroutine is applied. In this arrangement, there is no monitoringavailable during operation for a fault that can develop then.

As described previously above, what is needed is a technique formonitoring a system during operations and for diagnosing a fault beforethe system is shut down. It is to this end that the present invention isdirected. Moreover, when the present invention is used as it will bedescribed, it provides other advantages not available and not evencontemplated by the prior arrangements.

OBJECTS AND SUMMARY OF THE INVENTION

Accordingly, it is a principal object of the present invention toprovide a technique for both monitoring the performance online anddiagnosing faults online for a direct current motor control systemduring the operations of a computer system printer with which such amotor is connected functionally.

It is also an object of the present invention to provide onlineperformance monitoring and fault diagnosis for the stacker form-feedrollers that are powered by a direct current motor in an impact lineprinter during the operation of such a printer.

Another object of the invention is to provide a technique for the earlydetection of feed roller control faults in an impact line printer of acomputer system, before a fault causes problems.

Briefly, the technique of the invention involves a microcode controlsystem that performs both real time monitoring and online faultdiagnosis for mechanical equipment having at least one component that isoperated by a direct current electric motor. The technique includes thesteps of selecting conditions of operation that correspond to acceptableequipment functioning, and monitoring these conditions during theoperation of the equipment. When a fault develops, the monitoringroutine initiates in real time a diagnosis subroutine which identifiesthe component causing the fault and establishes an error message toindicate the now identified component.

The above and other objects, features and advantages of the presentinvention will become more readily apparent from the following detaileddescription of the presently preferred embodiment as illustrated in theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating the respective mechanical partsof one type of equipment controlled by a microprocessor, as an aid indescribing the present invention.

FIG. 2 is a block diagram illustrating in more detail the environment inwhich the present invention is adapted to function so effectively.

FIG. 3 is a flow chart indicating the control and monitoring routineperformed by the microprocessor that is connected as shown in FIG. 1.

FIGS. 4, 4A and 4B are a flow chart indicating the fault diagnosissubroutine performed in real time while the equipment is online.

FIG. 5 is a block diagram illustrating respective mechanical partsconnected for two or more control systems to share a commonmicroprocessor.

FIG. 6 is a diagrammatic view in perspective illustrating a formsstacker as used in one embodiment of the present invention.

FIG. 7 is a perspective view of part of a line type of impact printer,for use as an aid in describing the present invention.

FIG. 8 is a side view of the operative part of a paper feed guide, as anaid in describing the environment that one form of the invention isadapted for use.

DETAILED DESCRIPTION OF THE INVENTION

While the online performance monitoring and fault diagnosis technique ofthe present invention may be used in conjunction with a variety ofmechanical equipment, it will be described, for the purpose ofillustrating the invention, as it is connected operably with a directcurrent motor of a paper stacker device that is used on a impact lineprinter. In this environment, the invention functions to preventproblems that develop when errors arise in the control of the feedrollers in a powered form stacker device, such as form jamming,misfolding, tearing and the like.

In FIG. 1 of the drawings, the reference numeral 10 identifies amicroprocessor connected to a microcode driven motor drive device 11 foroperating a direct current motor 12. The microprocessor 10, found to beentirely satisfactory in performing as will be described in more detailhereinafter, is an INTEL 8051, available commercially from the IntelCorporation.

When cost becomes a significant factor, the direct current motor 12 isselected as a brush type device, but other types may be more suitable inother and different operating environments. Reliability can be increasedby using suitable gears to connect the direct current motor 12 to thefeed rollers 13 of a power form stacker used in conjunction with animpact line printer.

A motion sensor 14 is connected to detect motion in the feed rollers 13and to transmit such information by a connection 15 back to themicroprocessor 10. An important function of the feed rollers 13 is tomove forms at a constant velocity from the impact line printer into apowered form stacker mechanism. One voltage sense connection 16 and onecurrent sense connection 17 provide information to the microprocessor 10concerning the operational state of the motor drive 11 and the directcurrent motor 12.

A main microprocessor 18 is connected to the microprocessor 10 toinitiate control signals to it and to receive signals from themicroprocessor 10 by means of a communications bus 18a, indicatinginformation concerning the state of the system being monitored and anyresults of the fault diagnosis subroutine. A suitable display panel 19provides a convenient way of showing such information, all of which willbe described in more detail presently.

The mechanical portion of a computer line type printer environment inwhich the present invention is adapted to function will be described indetail presently. To describe a circuit control constructed inaccordance with the principles of the invention, reference is made toFIG. 2 of the drawings.

In FIG. 2, a computer interface microprocessor 20 receives data from acomputer system (not shown) by means of a bus connection 21. Data fromthe microprocessor 20 is placed in a random access memory device 22,from which the data is available to the printer main microprocessor 23where it is read and interpreted.

Based on such data, the printer main microprocessor 23 assigns varioustasks to individual printer mechanism systems, such as for example, adisplay panel 24 (which is comparable to the display panel 19 in FIG.1), an error log on diskette 25, print hammer logic 26a and firemechanism 27, a print band mechanism 29 (through an associatedmicroprocessor 28), a print carriage mechanism 32 (including its controlmicroprocessor 31) and a task microprocessor 33 controlling a paperstacker feed roller mechanism 34 and a stacker tray mechanism 35.

The stacker feed roller mechanism 34, in FIG. 2, consists of the motordrive 11, the direct current motor 12, the feed roll unit 13 and themotion feedback sensor 14, as shown in FIG. 1.

The printer main microprocessor 23 monitors the respective printermechanisms for status, resolves conflicts relating to communications ona main bus 36, performs error logging on the diskette 25 and providesdata indicating status to the computer interface microprocessor 20. Eachof the printer mechanism control systems manages the unique, real timecontrol of its mechanical function.

Tasks are received from the printer main microprocessor 23, interpretedand executed at the correct time by the individual task microprocessors28, 31 and 33. In addition to functional control, each taskmicroprocessor 28, 31 and 33 provides online error detection and faultdiagnosis (isolation) via real time state checking of various sensepoints (or hooks, or signals) in the controlled mechanism, via real timecontinuous performance monitoring (or velocity checking), or via both.This is done over bus connections 37a, 37b, 38, 39a and 39b, FIG. 2.

When an error condition is detected, a fault diagnosis subroutine isperformed and a shutdown procedure is initiated on the failingmechanism. At this point, an error status is reported to the printermain microprocessor 23 over the communications bus 36. The printer mainmicroprocessor 23 manages the shutdown of the other mechanisms if thatis necessary, reports the status to the computer interfacemicroprocessor 20, displays a status message on the display panel 24through the interface logic 26b and creates an entry through theinterface logic 26b in the printer internal error log, which is on thediskette 25.

FIG. 3 of the drawings shows that the feed roller control system is aclosed loop, frequency modulated drive for the direct current motor 12(FIG. 1). The microprocessor 10 (FIG. 1) monitors feed roller velocity(note, in FIG. 3, blocks 40 and 41) by means of the feedback connection15 which, for the particular use being described, is two feedback pulsesfor each revolution of the feed rollers, and the microprocessor 10modulates the drive signal frequency (note block 42) as any adjustmentappears to be necessary, which is based on any deviation in feed rollervelocity from a preset velocity or velocity range (note block 43).

On motor start-up, a microcode controls the acceleration, which is inthe control storage of the microprocessor 10. However, in accordancewith the invention, this motor start-up is checked by the microprocessor10, through the means of the feedback connection 15, to ensure that thefeed rollers accelerate from rest to servo velocity (note blocks 44 and45) within a preset period of time (note block 46).

Nominal acceleration time for unloaded (or zero drag force) feed rollerscan be 12 milliseconds. Should the feed rollers fail to reach the presetminimum velocity within the preset period of time, an error (or fault)is said to exist (note block 47), and the fault diagnosis subroutine ofFIG. 4 is initiated.

Before describing the fault diagnosis subroutine, it should be pointedout that other conditions can be identified and preset, with presetrange amounts, in order to initiate the fault diagnosis subroutine ifthey are deviated from for a preselected number of corrections. Forexample, after the feed rollers reach a preset servo velocity, the motordrive microcode, from the microprocessor 10, FIG. 1, begins controllingthe steady-state (or servo) velocity of the feed rollers.

By means of the microprocessor 10, the velocity of the feed rollers ischecked to ensure that it remains within a preselected range, or window(note block 43). If the velocity of the feed rollers remains outside ofa preselected range of permitted deviation for a predetermined number ofcorrection drive pulses (note block 48), for example 12 pulses, then afault is said to exist, and the fault diagnosis subroutine is entered(note block 47) in order to identify the fault further, as will bedescribed in more detail presently.

Another condition that can be preset is whether the feed rollers are ina certain state, such as "idle" or "stopped". For example, if the feedrollers are supposed to be in an idle state, the feed rollers can bechecked by means of the connection 15 for motion, which if motion isdetected and such detected motion exceeds a predetermined number ofpermitted revolutions, an error condition exists, and the faultdiagnosis subroutine is initiated. Actually, there are two ways todetect this error . . . 1) "speed" of motion (RPM) and "distance"(number of revolutions).

Of course, motion feedback over the connection 15, FIG. 1, is monitoredcontinuously, whether the equipment is running or stopped. For example,when the motor 12 is running, there must be a feedback signal on theconnection 15, and when the motor 12 is stopped, no significant feedbackshould be occurring on the connection 15. When the equipment is started,it must accelerate to a predetermined velocity within a preset period oftime, and also, when the equipment is running at its steady-statevelocity, it must remain within a predetermined range of permitteddeviations over a preset number of corrections.

Some of the errors in motor velocity are isolated by the microprocessor10 analyzing the motor driver voltage and current sense signalson-the-fly. In this instance, a fault isolation subroutine is executedimmediately.

In order to isolate a fault to a particular part or component, a faultdiagnosis subroutine is initiated, as will now be described inconjunction with FIG. 4 of the drawings. The fault diagnosis is executedon-the-fly, that is, before stopping the feed rollers and terminatingoperations of the equipment.

In accordance with the particular equipment being described forillustrative purposes, the fault diagnosis subroutine is initiatedwhenever a fault (or error) is detected indicating (1) feed rollerfeedback pulses are not occurring, (2) feed roller acceleration isexcessively slow, (3) feed roller motor velocity is too slow, or (4)feed roller motor velocity is too fast.

Upon initiation of the fault diagnosis subroutine, an error message isset up for one of the four error conditions identified above and inblock 49, FIG. 4. On-the-fly fault diagnosis now is initiated, and if aninterrogated signal does not correspond to a preselected "acceptable"condition, an error message is given to identify a specific part orcomponent as being responsible for the fault. The specific part orcomponent that is identified as responsible for the fault is shown inFIG. 4 as (1) a short circuited motor driver (note block 50), (2) motordrive signal stuck-at-faults (note blocks 51 and 52), (3) an opencircuited motor (note block 53), and (4) an open circuit motor driver(note block 54).

Before the next motor drive signal is initiated, the input/output portregister of the microprocessor 10 is read to determine the state of themotor drive signal from the microprocessor 10 and motor driver currentsense signal from the connection 17, FIG. 1, (note block 55 in FIG. 4).If the current sense signal from the connection 17 indicates current isnot flowing in the motor drive 11 and, therefore, in the direct currentmotor, FIG. 1, (note block 56 in FIG. 4), this indicates an acceptablecondition and the fault diagnosis subroutine continues after the nextmotor drive signal is initiated (note block 57 in FIG. 4).

After the motor drive signal is initiated, the motor drive signal fromthe microprocessor 10 and the motor driver voltage sense signal on theconnection 16 are read (note block 58). If the driver voltage sensesignal indicates that the motor driver is conducting (note block 59),this is an acceptable condition, and the fault diagnosis continues byinterrogating the motor driver current sense signal on the connection 17(note block 60). If current is sensed, this indicates an acceptablecondition, and the motor drive signal from the microprocessor 10, FIG.1, the motor drive 11 and the direct current motor 12 are all verifiedas being "good" to the main microprocessor 18 for appropriate indicationon the display panel 19.

Now, feed roller motion can be stopped by terminating the feed rollerdrive signal, and the initial error message is reported to the printer'smain microprocessor 18, FIG. 1, and 23 in FIG. 2 (note block 61 in FIG.4) over the communications bus 18a, FIG. 1, and 36, FIG. 2. The mainmicroprocessor 18 controls operations to stop the printer by issuingshutdown signals over the communications bus 36 in FIG. 2 to the othertask microprocessors 28, 31 and 33 in FIG. 2; it saves the error messagethrough the interface logic 26b, FIG. 2, in the printer's internal logon the diskette 25, also in FIG. 2; and it displays an error statusmessage through the interface logic 26b, FIG. 2, on the printer'salphanumeric operator display panel 19, FIG. 1, and 24 in FIG. 2.

On the other hand, if current is sensed in the motor driver 11 and inthe direct current motor 12, FIG. 1, (back to block 56 in FIG. 4), andif the motor drive signal is "off" (note block 62), and if the initialerror detected is servo "velocity fast" (note block 63), the errormessage is changed to indicate a short circuited motor driver (noteblock 50). Otherwise, the initial error message is unchanged.

If current is sensed (at block 56) and if the motor drive signal is not"off" (at block 62), the error message is changed to indicate amicroprocessor I/0 port register drive signal bit stuck-at-fault (noteblock 51).

If, after the drive signal is initiated (note block 58), the drivervoltage sense indicates that the driver is not conducting (note block59) and the motor drive signal is "on" (block 64), the error message ischanged to indicate an open circuited motor driver (block 54).

If the motor drive signal is "off" (block 64), the error message ischanged to indicate a microprocessor I/0 port register drive signal bitstuck-at-fault (block 52).

Operations Summary

Due to the complicated nature of the above described detailed procedure,the following abbreviated summary of some of the more significant stepsin the technique of the invention may be helpful:

During Start-up

At the time of start-up of the feed rollers, the rotational velocity ofthe rollers is checked to ensure that the rollers accelerate from restto the preset servo velocity within a preset period of time. If theservo velocity is not attainable, a fault diagnosis subroutine isinitiated.

During Operation

After the feed rollers reach their preset velocity, their velocity ischecked to ensure that the velocity remains within a preselected rangeof velocity deviation. If a velocity deviation remains outside of therange of acceptable deviation for a preset number of correction drivepulses, a fault diagnosis subroutine is initiated.

When Stopped

When the feed rollers are in a "stop" state, they are checked to ensurethat no significant motion is detected. If motion exceeds apredetermined number of revolutions, or revolutions per minute, noadditional fault diagnosis is necessary, and an error message isreported directly.

Advantages

The advantages of a technique in accordance with the invention includethe following:

1. Feed roller control and mechanism faults are not permitted to resultin paper jams, excessive misfolds and paper tears without reasonsavailable for correction.

2. Once a fault is detected, operations continue for one more motordrive pulse. During that interval, motor current and motor driver sensesignals are sampled and problems are diagnosed. By diagnosing faults inthis manner:

a) Improved fault isolation is achieved.

b) The problem part or component is identified.

c) Microprocessor utilization for the task of error detection isminimized, because only one signal is monitored continuously in realtime for preselected error conditions.

d) For the case of two or more control systems sharing a commonmicroprocessor, the direct current motor driver voltage and currentsense signals can be connected together in a "DOT-ORed" arrangement,provided that, at the time of sampling, these signals are inactive forall except the motor control system being diagnosed; that is all exceptthe diagnosed motor control system must be in a "stopped" state. Thisadvantage is illustrated in FIG. 5 of the drawings.

Referring now to FIG. 5, this figure illustrates, partially, anarrangement such as shown in more detail in FIG. 1. Using similarreference numerals to identify the respective components in FIG. 5, astacker feed roller control system includes a microprocessor 10a, 11a,12a, 13a and 14a: voltage and current sense signal connections 16a and17a. This stacker feed roller control system is "DOT-ORed" with astacker tray control system which includes the components 10a, 11b, 12band 13b as well as the voltage and current sense signal connections 16aand 17a.

This view in FIG. 5 shows that it is within the purview of the inventionto control a plurality of systems from a common microprocessor.

This can readily be the same mechanical equipment in FIG. 5 and caninclude the same or similar feedback connections, such as the feedbackconnection 15 that is illustrated in FIG. 1. Also, there can be, in themodification of FIG. 5, a main microprocessor 18 and a common displaypanel 19, like those in FIG. 1.

FIG. 5 shows a single microprocessor 10a connected as a control systemfor the motor drive 11a and also as a control system for the motor drive11b. There is illustrated, in addition, a direct current motor 12a and adirect current motor 12b. However, FIG. 5 illustrates common voltage andcurrent feedback connections 16a and 17a which can be used with anarrangement in accordance with the present invention.

FIG. 6 of the drawings illustrates diagrammatically a power formsstacker with which the invention is adapted to function effectively, andFIG. 7 illustrates the operative components of an impact line printer.FIG. 8 shows a forms stacker device with which the invention functionsalso. Legends on these figures identify the various parts.

Fault Isolation Pseudo Code For Online Fault Diagnosis

An assumption is that prior to entering this procedure, either (A) or(B) has occurred.

(A) During acceleration, either 1) no feedback pulses have occurred, or2) feedback pulses are occurring, but servo motor velocity has notreached within a specified period of time.

(B) During operations, the feed roller velocity was outside thespecified range for acceptable conditions.

Therefore, the following fault diagnosis procedure, shown also in FIG.4, is initiated online in real time:

    ______________________________________                                        PROCEDURE;                                                                      IF no feedback signal was received during                                     acceleration, THEN                                                            Error Status = no feed roller motion detected.                                 Go to DRIVER.sub.-- TEST (block 49, Item 1, FIG. 4)                          END IF:                                                                       IF a feedback signal was received, but servo                                  velocity was not achieved, THEN                                               Error Status = feed roller acceleration slow.                                  Go to DRIVER.sub.-- TEST (block 49, Item 2, FIG. 4).                         END IF;                                                                       IF velocity was outside acceptable range & fast,                              THEN                                                                          Error Status = feed roller velocity fast.                                      Go to DRIVER.sub.-- TEST (block 49, Item 4, FIG. 4).                         END IF;                                                                       IF velocity was outside acceptable range & slow,                              THEN                                                                          Error Status = feed roller velocity slow.                                      Go to DRIVER.sub.-- TEST (block 49, Item 3, FIG. 4).                         END IF;                                                                     DRIVER.sub.-- TEST:                                                             DO;                                                                            Read the feed roller current sense signal.                                   (block 55, FIG. 4)                                                            IF current is flowing (block 56, FIG. 4),                                     THEN                                                                           Read the feed roller I/O drive signal                                          port bit (block 55, FIG. 4).                                                 IF feed roller run bit = on (block 62,                                        FIG. 4), THEN                                                                  Change error status = I/O port                                                      failure.                                                                      Failure mode =                                                                 I/O register                                                                  bit stuck on.                                                               (block 51, FIG. 4)                                                     Go to DIAGNOSIS.sub.-- DONE (block 61, FIG. 4)                                END IF;                                                                       IF error is not velocity fast (block 63),                                     THEN                                                                          Go to DIAGNOSIS.sub.-- DONE (block 61)                                        ELSE;                                                                           Change error status = Feed roller                                                   driver failure.                                                                Failure mode =                                                               shorted or low                                                                resistance driver.                                                            (block 50)                                                              Go to DIAGNOSIS.sub.-- DONE (block 61)                                       END IF;                                                                      END IF;                                                                     DO;                                                                             Send Drive Pulse (block 57, FIG. 4).                                          After next drive pulse, read feed roller driver                               voltage sense (block 58, FIG. 4).                                             IF driver not on (block 59),                                                  THEN                                                                           Read I/O drive signal port bit (block 58).                                    If feed roller run bit = OFF (block 64),                                      THEN                                                                          Change error status = I/O port failure.                                              Failure mode = I/O                                                            register bit stuck off.                                                       (block 52, FIG. 4)                                                      Go to DIAGNOSIS.sub.-- DONE (block 61, FIG. 4)                                END IF;                                                                      ELSE;                                                                          Change ERROR status = Feed roller driver                                            failure.                                                                      Failure mode = open or                                                        high resistance driver.                                                       (block 54)                                                              Go to DIAGNOSIS.sub.-- DONE                                                  END IF;                                                                      END DO;                                                                       Read feed roller current sense (block 60, FIG. 4).                            IF current not flowing (block 60 -a, FIG. 4),                                 THEN                                                                           Change ERROR status = Feed roller                                                    motor or driver failure.                                                      Failure mode = open motor or                                                  driver card connector.                                                        (block 53)                                                              Go to DIAGNOSIS.sub.-- DONE                                                   END IF;                                                                     END DO;                                                                       DIAGNOSIS.sub.-- DONE:                                                         DO                                                                            Shut Down Feed Rollers (block 61, FIG. 4).                                    Report Error Status (block 61).                                               END DO;                                                                    END PROCEDURE;                                                                ______________________________________                                    

The invention has been shown, described and illustrated in substantialdetail with reference to a presently preferred embodiment thereof and amodification of that embodiment. It will be understood by those skilledin this art that various changes and further modifications may be madewithout departing from the spirit and scope of the invention which isset forth in the claims appended hereto.

What is claimed is:
 1. In a control system for controlling mechanicalequipment having, in combination, at least one direct current electricalmotor and at least one operating component connected for functionaloperation thereby, said control system having a routine for monitoringin real time preselected conditions in said equipment, a method ofperforming real time diagnosis of a fault condition comprising the stepsof:selecting conditions of operation corresponding to acceptableequipment functions; monitoring said conditions during the operation ofsaid equipment; initiating a fault diagnosis subroutine in real time,while said equipment operation is continuing, when a monitored conditiondeviates from a condition selected as being acceptable; identifyingwhich of said selected conditions from which said monitored conditiondeviates; and establishing an error message to indicate the identifiedcondition while said equipment is operating.
 2. The method of claim 1including the steps of establishing a range of acceptable deviations forsaid selected conditions, and initiating said fault subroutine when saidmonitored condition deviates from said range.
 3. The method of claim 1including the steps of establishing a servo motor velocity as one ofsaid acceptable conditions, and selecting a range of deviations fromsaid servo motor velocity as being acceptable before said faultsubroutine is initiated.
 4. The method of claim 1 including the step ofadjusting a condition detected by said monitoring as being unacceptableto bring said unacceptable condition within a predetermined range ofacceptable deviation.
 5. The method of claim 4 including the steps ofchecking said condition detected as being unacceptable again after saidstep of adjusting to determine whether said unacceptable condition ismade acceptable, and initiating said fault diagnosis subroutine onlywhen said condition is still unacceptable.
 6. The method of claim 1including the steps of establishing a range of acceptable deviations forsaid selected conditions, and said step of monitoring including themonitoring of said range of acceptable deviations.
 7. The method ofclaim 6 including the step of initiating said fault diagnosis subroutineonly when an unacceptable condition is detected as being outside saidrange.
 8. The method of claim 1 including the steps of establishing apredetermined range of servo motor velocities as acceptable conditions,and monitoring said predetermined velocity range.
 9. The method of claim1 including the steps of establishing a range of acceptable accelerationdeviations as an acceptable condition, and monitoring acceleration ofsaid direct current motor during startup operation of said equipment.10. The method of claim 1 including the steps of establishing a numberof revolutions and a permitted revolutions per minute for additionalones of said acceptable conditions for said direct current motor when ina stopped position, and monitoring said range for a deviation from saidrange of acceptable revolutions, and initiating said fault diagnosissubroutine in real time when said range is exceeded.
 11. A method ofperforming real time diagnosis of a fault condition in a system having aroutine for monitoring preselected conditions in real time forcontrolling mechanical equipment with electrical motor means foroperating predetermined functions, said method comprising:selectingconditions of operation that corresponds to acceptable equipmentfunctions; monitoring said conditions during the operation of saidequipment; initiating a fault diagnosis subroutine in real time, whilesaid equipment operation is continuing, only when an unacceptablecondition is detected by said monitoring of said conditions; andidentifying said unacceptable condition detected by said monitoring,including identifying a component causing said unacceptable condition,during continuing operation of said equipment.
 12. The method of claim11 including presetting a range of deviation for each acceptablecondition selected.
 13. The method of claim 11 including presetting arange of deviation for each acceptable condition selected, andinitiating said fault diagnosis subroutine when said monitored conditiondeviates from said range.
 14. The method of claim 11 including adjustinga condition detected as being unacceptable to correct a deviation fromsaid acceptable equipment function.
 15. The method of claim 11 includingthe steps of presetting a range as acceptable conditions; monitoringsaid range of acceptable conditions in real time; and initiating saidfault diagnosis subroutine while said equipment is operating when saidrange is exceeded.